Punctal Dilation and Mini-Monoka Stent Insertion

Procedure: This video demonstrates punctal dilation and insertion of a Mini-Monoka stent for treatment of epiphora due to punctal/canalicular stenosis. Introduction: Nasolacrimal stents are tubes that are placed within the nasolacrimal system to maintain patency. There are several different types of lacrimal stents; some are monocanalicular and others are bicanalicular. Indications/Contraindications: Nasolacrimal stenting is indicated in nasolacrimal stenosis or obstruction, trauma, and post-surgical osteotomy maintenance. Patients with canaliculitis are often not irrigated or stented due to the friability of the infected tissues¹. Materials/Methods: A punctal dilator, Mini-Monoka stent, small scissors, and small forceps are required for this procedure. Results: Mini-Monoka stents have been shown to provide significant symptomatic improvement in most (>80%) patients with punctal and canalicular stenosis². Intubation of the nasolacrimal system is usually temporary, with stents removed after several weeks to months. Conclusions: Mini-Monoka punctocanaliculoplasty is a minimally invasive and often effective treatment strategy for management of epiphora secondary to upper nasolacrimal stenosis.

The nasolacrimal system is responsible for the flow of tears from the medial canthus to the nasal cavity. Nasolacrimal stents are silicone tubes that are placed within the nasolacrimal system to maintain patency. Stenting is indicated in nasolacrimal stenosis and obstruction, trauma, and post-surgical osteotomy maintenance. Nasolacrimal obstruction can be secondary to infection, inflammation, chemotherapy, trauma, radiation, thermal injury, congenital malformations, and iatrogenic causes. In an incompletely stenosed or obstructed system, nasolacrimal stents can be placed following nasolacrimal dilation and probing to stretch the system for several weeks. In settings of complete canalicular obstruction, a lacrimal (Sisler) trephine is used to perform rotary trepanation followed by canalicular stenting for 9-12 months. 5-fluorouracil and docetaxel are chemotherapeutic agents commonly used in colon, gastrointestinal, and breast cancers which have been documented to cause canalicular stenosis3. Radioactive iodine for treatment of papillary thyroid carcinoma is associated with lower lacrimal system obstruction. In patients receiving frequent doses of chemotherapy, canalicular stents can be prophylactically inserted at the first symptom of recurrent or progressive epiphora to prevent permanent upper nasolacrimal system scarring. Regarding congenital nasolacrimal obstruction, initial treatment is probing and irrigation, which is often highly successful4,5. In unsuccessful cases, a lacrimal stent inserted from the punctum to inferior meatus and retrieved through the nostrils can be used to stretch the nasolacrimal system6.  Cases which fail conservative management, often in children older than 19 months, could be considered for a balloon dacryoplasty or full dacrocystorhinotomy7. Monocanalicular stents intubate either the upper or lower canaliculus while bicanalicular stents pass through both upper and lower canaliculi and create a closed circuit. One commonly used monocanalicular stent is the Monoka stent, a silicone tube that comes in two sizes (full-size and mini). It is anchored at the punctum by a plug on one end. Bicanalicular stents include the Crawford, Ritleng, pigtail/donut, and Kaneka Lacriflow stents. In cases where the upper lacrimal system is not able to be canalized, a Pyrex glass Jones tube may be surgically placed through the caruncle and then through a bony ostium which exits into the middle meatus of the nose.

Preoperative workup: Prior to performing the procedure, a thorough history and complete eye exam with slit lamp biomicroscopy should be performed with a focus on the lacrimal system. The lacrimal puncta should be inspected for size and patency and apposition to the globe. The height of the tear lake and dye disappearance should be assessed as well. Other causes of epiphora should be ruled out, such as dry eye. Instrumentation/Setup: A punctal dilator, Mini-Monoka stent, small scissors, and small forceps are required for this procedure. The Mini-Monoka stent is a medical-grade silicone rod that is both inert and flexible. It measures 40mm in length and 0.64mm in width. There is a bulb and collar at the proximal end, which makes it self-retaining. Anatomy and landmarks: The puncta are the entrances to the lacrimal drainage system and are located on the medial margins of the upper and lower eyelids. They open into the superior and inferior ampullae, which are about 1-2mm in vertical height. From the ampullae, the lacrimal system makes a 90 degree turn into the horizontal canaliculi, which run 8-10mm medially. Most people have the superior and inferior horizontal canaliculi meet and form a common canaliculus that enters the lacrimal sac. The valve of Rosenmüller is a membrane which functions as a one-way valve to prevent reflux from the lacrimal sac into the canaliculi. The lacrimal sac extends inferiorly around 10mm and forms the nasolacrimal duct, which runs through the maxilla and is about 12mm in length. The nasolacrimal duct opens into the nose through an ostium in the inferior meatus and contains a distal valve (the valve of Hasner). Procedure steps: A punctal dilator is used to dilate the puncta. The punctal dilator is initially introduced vertically into the punctum and then rotated horizontally. As the dilator is being inserted, lateral traction is applied to the eyelid to straighten the canaliculus and allow passage of the punctal dilator horizontally. Following dilation, probing and irrigation should be performed to ensure that the canaliculus is patent. Prior to insertion, the Mini-Monoka stent should be trimmed, leaving a beveled edge, to cover the area of pathology and slightly beyond. The stent is then introduced into the canaliculus using a small forceps and advanced so that only the bulbed end is visible. For the final step of insertion, the cap is grasped firmly with the forceps and the punctal dilator is inserted into the hole in the cap. The bulb is then carefully rotated with the punctal dilator so that it sits firmly inside the punctum.

If the upper nasolacrimal system is patent and the puncta and canaliculi can be dilated, the success rate of nasolacrimal stent placement is very high, often > 90%^8,9. Mini-Monoka stents have been shown to provide significant symptomatic improvement in many (>80%) patients with punctal and canalicular stenosis². Besides stent dislodgement, complications of stent insertion include stent prolapse in bicanalicular stents resulting in a loop protruding from the puncta, damage to the puncta due to excess tension, trauma to the canalicular system, granuloma formation, and infection of the nasolacrimal drainage system. Following insertion, the Mini-Monoka stent is usually left inside the nasolacrimal system for several weeks prior to removal in an outpatient setting. Monocanalicular stents such as the Mini-Monoka are removed by pulling them out with forceps.

Mini-Monoka punctocanaliculoplasty is a minimally invasive and often effective treatment strategy for management of epiphora secondary to upper nasolacrimal stenosis. Prior to any stenting procedure, one must consider the advantages and disadvantages of monocanalicular and bicanalicular stenting. One advantage of the Mini-Monoka stent compared to the bicanalicular Crawford tube is that the Mini-Monoka stent can be placed in a clinical setting without sedation. Insertion of the Crawford tube often requires anesthesia due to manipulation of the nasal cavity. There is also a risk of bleeding during Crawford tube insertion, so it is not the ideal treatment in patients with bleeding abnormalities. Compared to the Crawford tube, the Mini-Monoka tube has a higher risk of falling out and may not be the optimal choice in children.

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